SCIENCE SAYS, YOU CAN'T BEAT GENETICS
The parenting myth: How kids are raised matters less than you think
DNA is more important to a child’s personality, exam results and future income than the way they are brought up – but that’s good news, says geneticist Robert Plomin
IT IS an age-old question: are we shaped more by nature or nurture? Robert Plomin, a geneticist at King’s College London, has spent his career teasing apart the contributions of DNA and environmental factors to countless human traits, from body weight to personality and academic success. Environment is undoubtedly a key influence on almost every aspect of our lives. But Plomin argues that genetics plays a more important and measurable role, even to the extent that our parenting and schooling don’t matter that much. We caught up with him to discuss his sometimes controversial views. Give us an example showing how little influence parenting has on the way children turn out. Take our propensity to be overweight. If zero means parents have no influence and one means total influence, when two siblings grow up together, their body mass index has a correlation of about 0.4. It’s easy to see how people attribute that mainly to nurture, because parents provide both siblings with the same food. But it turns out that isn’t true, and obesity runs in families for reasons of genetics. A killer piece of data is that the correlation for weight is 0 between adoptive siblings who grow up in the same family but don’t share genes. Even more striking is that if you were adopted at birth away from your sibling, you correlate just as much as if you had been reared together in the same family. Is this true for intelligence and personality too? Definitely for cognitive abilities. There aren’t as many studies on personality, but we know that identical twins reared apart are as similar in personality as identical twins reared together. I’ve studied identical twins who have grown up apart, and I find it amazing how they are so similar in things like the way they laugh or talk. What do these findings mean for who we are, and who we become? Twin and adoption studies have shown us that about half the differences between people in any trait you want to name is due to DNA differences, and half isn’t. But whatever the environment is, it makes two kids in the same family as different as those in two different families. The effects of the environment are random. The implications of these findings are enormous because it means inherited differences are the major systematic [non-random] force in making us who we are.
newscientist.com
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